intersection-of-two-arrays-ii-counter.py

# https://leetcode.com/problems/intersection-of-two-arrays-ii/

# Given two arrays, write a function to compute their intersection.

from unittest import TestCase
from collections import Counter


def intersect(nums1, nums2):
    """
    :param nums1: List[int]
    :param nums2: List[int]
    :return: List[int]
    """

    count_nums1 = Counter(nums1)
    count_nums2 = Counter(nums2)
    result = []

    for num, count in count_nums1.items():
        if num in count_nums2:
            nr_repeated_intersections = min(count, count_nums2[num])
            result.extend([num] * nr_repeated_intersections)

    return result


class TestIntersect(TestCase):
    def test_with_repeated_number_both_lists(self):
        self.assertEqual([2, 2], intersect([1, 2, 2, 1], [2, 2]))

    def test_with_multiple_repeated_numbers_both_lists(self):
        self.assertEqual([4, 9], intersect([4, 9, 5], [9, 4, 9, 8, 4]))

    def test_list_with_repeated_numbers_matching_to_one_number_in_other_list(self):
        self.assertEqual([1], intersect([1, 1], [1, 2]))

    def test_list_with_repeated_numbers_matching_to_a_list_with_unique_number(self):
        self.assertEqual([2], intersect([1, 2, 2, 1], [2]))